It isn't finished yet, but it was opened to the public a few days ago. I went inside for the fist time this evening after work.
I think it's the best thing built in New York since the 1930 Chrysler Building. The interior isn't as good as the exterior though. The columns feel too straight inside - the elegant curve that they make when they turn into the bird's wings cannot be seen there. The interior view begs to be unfavorably compared to Gothic cathedrals. The exterior holds its own against the best-looking representatives of the Aves class.
I've been following skyscraperpage.com (which is about architecture in general, not just skyscrapers) almost daily for at least a decade now, and Calatrava is the best living architect I'm aware of. Here's a Google image result for his works.
I think that public Western architecture is finally seeing a recovery from the bottom that it reached in the 1940-2000 period. This is weird because people don't seem to be dressing any better than they did in the late 20th century. I haven't noticed any improvement in the aesthetics of furniture or household appliances either. Ugly public art was a part of the leftist political trend. Leftism is still on the rise - gay marriage, the erosion of the nation state, etc. But for some reason architecture is slowly sliding back to sanity.
Robert A.M. Stern's new buildings are downright traditional-looking. There's been a move away from the awful towers-in-the-park model (think public housing) back to the ancient street-wall model of city planning. You can actually see it in the new World Trade Center, among many other developments here in New York and elsewhere.
I don't have an explanation for this de-coupling of architecture from general societal trends. But it's an interesting phenomenon.